The family SUV appeared to be packed for a road trip and a fun summer day at a water park.

There were beach towels and a cooler in the back, paperback books tucked into seat pockets. A young girl’s shoes had been removed and sat empty on the floorboard.

But hundreds of gruesome crime scene photos viewed by the Will County jury in the Christopher Vaughn trial this morning portrayed the horror that investigators found inside the vehicle early on the morning of June 14, 2007.

Vaughn’s wife, Kimberly, was in the front passenger seat, slumped to one side, a bullet wound beneath her chin. Behind her, the bodies of the couple’s three children were all slumped forward, their seat belts still buckled.

Shattered glass and shell casings littered the floor. Blood splattered almost every corner of the vehicle. And a trail of blood led a few hundred feet down the spider-cracked frontage road where Vaughn, bleeding from minor gunshot wounds to his wrist and thigh, had flagged down a passing motorist.

Vaughn, 37, is on trial on charges he gunned down his wife, daughters Abigayle, 12, and Cassandra, 11, and son Blake, 8, so he could start a new life in the Canadian wilderness. Defense attorneys have blamed Vaughn’s wife, saying she was distraught over troubles in her marriage and killed the children, wounded Vaughn, then committed suicide.

The photos being shown to the jury today mark the beginning of what is expected to be a complex forensics puzzle that prosecutors believe will poke holes in Vaughn’s claims of innocence.

As Illinois State Police investigator Robert Deel described in detail each of the more than 100 photos he took of the crime scene and later at the morgue, the gory images were displayed on a large-screen television in the courtroom and also on a smaller monitor on the defense table.

Vaughn, dressed in a beige blazer, sat calmly as the photos were displayed, his mouth set in a flat expression. He scribbled notes on a legal pad but didn’t appear to look at the screen.

Deel is a former crime-scene investigator who was at the center of both the Vaughn and Drew Peterson cases, which are being tried simultaneously in adjacent courtrooms at the Will County courthouse in Joliet.

Deel was criticized for his investigation into the 2004 drowning death of Peterson's wife, Kathleen Savio, which was initially ruled an accident. Authorities later concluded the death was a homicide after Peterson's fourth wife, Stacy, went missing in October 2007. Deel testified in Peterson's trial earlier this month.

On Thursday, Judge Daniel Rozak barred Vaughn's attorneys from asking Deel about the Peterson investigation or allegations that he was sidelined in the Vaughn case because he was pushing State's Attorney James Glasgow to consider the possibility that Vaughn's wife, Kimberly, could have committed the shootings in a murder-suicide.

Vaughn's attorney, George Lenard, argued the information was relevant because it could show investigators had "tunnel vision" and sought early on to pin the murders on Vaughn.

But Rozak said whatever Deel's opinion was irrelevant for the jury.

"All that's going to do is muddy the waters," Rozak said in making his ruling.

Prosecutors argued that Deel was never removed from the Vaughn investigation. Addressing rumors that Glasgow had asked the state police to stop using Deel altogether on homicide investigations, Assistant State's Atty. Michael Fitzgerald pointed out that in 2008 Deel processed the scene of a mass murder at a Lane Bryant store in Tinley Park.